Flash lamps



July 20, 1965 l-:lzo GoTo ETAL 3,195,325

FLASHYLAMPS Filed March 26, 1962 United States Patent 3,195,325 FLASH LAMPS Eizo Goto, Chigasalri-shi, Narnia iwata, dawara-slii, and ifoichi Takahashi, Tokyo, Japan, assignors to Tokyo Shit-saura Electric Co. Ltd., Kawasaki, .iapang a corporation of apan Filed Mar. 26, 1962, Ser. No. 182,209 Claims priority, application Japan, Apr. 1, 1961, 13d/11,177 3 Claims. (Cl. 67-31) The present invention relates to flash lamps and more particularly to novel and improved flash lamps having a greatly extended effective flashing time.

Various flash lamps have been proposed and in -use which employ as their light-emitting element threads of zirconium, which are characteristically high in light output and low in shock against the lamp wall when they are fired. Such light-emitting element of zirconium, however, has a very high rate of combustion, which further increases as the pressure of the combustion-promoting gas enclosed in the lamp bulb is increased as when the lamp bulb is reduced in size. Under these circumstances, it has been difficult to realize an effective flashing time of a length as required, for example, with flash lamps of the FP class.

Various attempts have been made to overcome the above difficulty. For instance, with flash lamps employing a light-emitting element sealed in the bulb and including two kinds of threads, one having a smaller diameter and the other having a larger diameter, it has been proposed to delay the ignition of the larger-diameter threads by controlling the quantity and composition of the igniting lagent. With this type of flash lamps, it has also been proposed to reduce the rate of combustion of the thicker threads by further increasing the diameter thereof. The former method, however, is apparently not so effective to extend the effective flashing time of the flash lamp to any substantial extent and involves the danger of misfiring. In the latter method, it is necessary to increase the thread diameter to an extreme extent for any satisfactory reduction in the rate of combustion. Such extreme diameter of threads, made of a heavy and less flexible material such as zirconium, may detract from the uniformity in quality of flash lamps employing such threads since it is rather diiicult to accurately introduce the desired quantity of such thread material into the lamp bulb for example by suction of an air stream. Moreover, the threads thus introduced into the bulb tend to be distributed therein so as to be denser in the vicinity of the bulb Wall, which involves the danger of incomplete combustion of such threads.

It is desirable, for example, with flash lamps of the FP class that they have a large light emission, a limited time lapse between the switching-in and the start of light emission, and also an effective flashing time which is suciently long. We have made investigations taking notice of the fact that the combustion of the lightemitting element may be retarded by admlxing an inert gas to the combustion-promoting gas sealed in the bulb, and have found that the effective flashing time may be materially extended without any substantial reduction in light quantity or any delay in starting light emission by admixing to the combustion-promoting gas comprising oxygen an inert gas such as argon in a proportion of approximately 1.5 to 15 percent.

These and other objects and advantages of the present invention will be apparent from the following description when read with reference to the accompanying draw- 2 ing, which illustrates diagrammatically one preferred embodiment of the invention.

In the drawing, there is shown a flash lamp according to the present invention which comprises a lamp bulb 3 having a diameter of approximately 33 millimeters and provided therein with a filament 1 and an igniting element 2. Sealed in the glass bulb is a light-emitting element 4 including two kinds of zirconium threads having a cross section of 20 x 15 microns and 35 x 30 microns, respectively. A combustion-promoting gas including oxygen admixed with approximately 10 percent of argon is then filled in the bulb. Compared with a similar flash lamp filled only with oxygen as a combustion-promoting agent, the flash lamp obtained with a mixture of oxygen and argon as described exhibits only an extremely slight increase in time lapse between the switching-in and the start of light emission, for example from approximately 3.3 milliseconds to 3.5 milliseconds and a very slight decrease in total amount of the light emitted, for example from approximately 22,000 lumens per second to 21,700 lumens per second. The effective flashing time, however, is materially increased by the addition of argon, for example from approximately 21.9 milliseconds to 34.7 milliseconds. It will be appreciated that the ash lamp fabricated according to the present invention has highly improved light-emitting characteristics, for example, for use as an FP class flash bulb.

Substantially similar results may be obtained by employing a rare gas other than argon, as for example neon or xenon. It has been found, however, that the use of a base gas such as nitrogen or nitrogen :suboxide leads to unsatisfactory results in that it causes -a marked reduction in the amount of light emitted owing to incomplete combustion of the light-emitting element, which results from a markedly increased proportion of' such inert gas in the mixture as required to extend the effective flashing time.

What is claimed is:

1. A flash lamp comprising a light transmitting bulb, ignition means disposed in the bulb, light emitting threads of zirconium sealed in the bulb, -and a combustion promoting gas and a rare gas component mixed in the amount of approximately 1.5 to 15 percent to extend the elective flashing time.

2. The flash lamp of claim 1 wherein the inert gas is selected from the group consisting of argon, neon and xenon.

3. The flash lamp of claim 1 wherein the elements of zirconium yare elongated having cross sections of two sizes; namely, 20 x 15 microns and 35 x 30 microns, the rare gas is argon in the amount of 10 percent and said flash lamp being characterized by an effective flashing time of approximately 35 milliseconds and a flashing time lapse of yapproximately 3.5 milliseconds.

References Cited by the Examiner UNITED STATES PATENTS 2,013,371 9/35 Van Liempt et al. 313-223 2,228,327 1/ 41 Spanner 313--223 2,272,779 2/42 Sarbey 67-31 2,334,155 11/43 Gram 67-31 2,351,375 6/44 Van Liempt et al. 67--31 2,874,030 2/ 59 Dennis 23-209 3,045,460 7/ 62 Brouse et al 67-31 EDWARD J. MICHAEL, Primary Examiner.

FREDERICK L. MATTEsoN, JR., Examiner. 

1. A FLASH LAMP COMPRISING A LIGHT TRANSMITTING BULB, IGNITION MEANS DISPOSED IN THE BULB, LIGHT EMITTING THREADS OF ZIRCONIUM SEALED IN THE BULB, AND A COMBUSTION PROMOTING GAS AND A RARE GAS COMPONENT MIXED IN THE AMOUNT OF APPROXIMATELY 1.5 TO 15 PERCENT TO EXTEND THE EFFECTIVE FLASHING TIME. 